Heat exchanger

ABSTRACT

The invention relates to a heat exchanger, in particular for a synthesis gas installation, for the heat exchange between a first and a second medium (W, G), comprising a shell ( 10 ), which is made to extend along a longitudinal axis (L) and bounds a shell space (M) for receiving the first medium (W), a tube space (R), which is surrounded by the shell space (M), for receiving the second medium (W), and a pass baffle ( 20 ), which is arranged in the shell space (M) and made to extend along the longitudinal axis (L), for directing the first medium (W), carried in the shell space (M), along the longitudinal axis (L). According to the invention, it is provided that the pass baffle ( 20 ) is welded to the shell ( 10 ).

SUMMARY OF THE INVENTION

The invention relates to a heat exchanger, in particular for a synthesisgas installation, for the (indirect) heat exchange between a first and asecond flowing medium, in particular in the form of feed water andsynthesis gas. In particular, the invention relates to a heat exchangercomprising: a shell which extends along a longitudinal axis and bounds ashell space for receiving the first medium, a tube space, surrounded bythe shell space, for receiving the second medium, and a pass baffle,which is arranged in the shell space and extends along the longitudinalaxis, for directing the first medium, carried in the shell space, alongthe longitudinal axis.

Such a heat exchanger has at least one pressure-bearing shell, which ismade to extend along a longitudinal axis and bounds a shell space forreceiving the first medium, and also has a tube space, which issurrounded by the shell space and in which the second medium isconducted, so that the second medium, carried in the tube space, canenter into indirect heat exchange with the first medium, on the shellside. To allow the first medium to be conducted through the shell space(and back) along the longitudinal axis, a longitudinal directing panelis provided, made to extend in the manner of a sheet along thelongitudinal axis and generally produced from a metal (pass baffle). Inother words, the pass baffle divides the shell space into two portions,a first portion and a second portion, that run parallel to one anotheralong the longitudinal axis, in order to extend the flow path of thefirst medium in the shell space and thereby intensify the heat exchange.Such a heat exchanger is known, for example, from U.S. Pat. No.4,778,005.

It is of great importance here that, when the heat exchanger isoperating in the way intended, as far as possible there are no bypassingflows that reduce the effectiveness of the heat exchange. In the case ofthe known heat exchanger, there is particularly the problem that, whenthere is a failure of the sealing of the pass baffles with respect tothe surrounding shell, such bypassing flows of the first medium canoccur, leading to a significantly lower heat exchange of the firstmedium in the shell space, which correspondingly reduces theeffectiveness of the heat exchange. Such a heat exchanger is thereforenot suitable in particular for applications at high pressures (forexample in synthesis gas installations).

Against this background, one aspect of the present invention is toprovide a heat exchanger that is improved with respect to theaforementioned problem.

Upon further study of the specification and appended claims, otheraspects and advantages of the invention will become apparent.

These aspects are achieved by a heat exchanger wherein the pass baffleis welded to the shell.

In accordance with the invention, the pass baffle of the heat exchangeris welded directly to the shell (i.e. is connected directly to the shellby means of a welded connection which may comprise a number of weldseams). This welded connection is impermeable in particular to the firstmedium, so that the first medium cannot pass from the first portion ofthe heat exchanger into the second portion of the heat exchanger by wayof that welded connection. This solution according to the inventionconsequently makes it possible in principle to reduce the risk ofso-called bypassing flows, and therefore have much better control overthe process.

The shell preferably has a first shell part, which is made to extendalong the longitudinal axis, and a second shell part, which is made toextend along the longitudinal axis and lies opposite the first shellpart transversely in relation to the longitudinal axis. The two shellparts are connected (welded) to one another by way of the pass baffle.The shell parts are preferably parts in the form of half shells, inparticular in the form of halves of a cylindrical shell (of a straighthollow-circular cylinder).

The pass baffle is preferably formed such that it is made to extendlongitudinally along the longitudinal axis and thereby preferably has asheet-like rectangular form, with two peripheral regions lying oppositeone another transversely in relation to the longitudinal axis andrunning along the longitudinal axis. These two peripheral regions,respectively, have a first side, which faces the first shell part, and asecond side, which is remote from the first side and faces the secondshell part.

The two shell parts preferably respectively have a first end face, whichis made to extend along the longitudinal axis. The first shell part ispreferably connected by its first end face, made to extend along thelongitudinal axis, to the first side of the first peripheral region byway of a first weld seam. The second shell part is preferably connectedby its first end face, made to extend along the longitudinal axis, tothe second side of the first peripheral region of the pass baffle by wayof a second weld seam. In the same way, the second end faces of the twoshell parts may also be respectively connected to the second peripheralregion of the pass baffle.

The weld seams preferably completely fill intermediate spaces betweenthe end faces of the shell parts and the respective peripheral regionsof the pass baffle. That is, in a cross-sectional plane runningperpendicularly in relation to the longitudinal axis of the shell, theweld seams connected to the peripheral region of the pass baffle arerespectively formed continuously (in one piece), so that the weld seamsrespectively have an outer side and an inner side. The outer side facesan outer space surrounding the shell, is adjacent thereto and goes overinto an outer side of the respectively assigned shell part of the shell.The inner side faces the shell space, is adjacent thereto and goes overinto an inner side of the respectively assigned shell part of the shellthat faces the shell space and goes over into the respectively adjacentside of the pass baffle.

In this case, in a cross-sectional plane running perpendicularly inrelation to the longitudinal axis of the shell, the weld seams inquestion may initially narrow towards the shell space and widen again,in particular in a step-shaped manner, in the region of an inner side,facing the shell space, of the respectively assigned shell part, so thatthe weld seams concerned respectively reach around a periphery of therespectively assigned end face of a shell part.

Furthermore, the thickness of the pass baffle may be narrowed towards anouter periphery, i.e. in particular at the two peripheral regions, thatis to say between end faces opposite from one another of the shellparts, or as an alternative to this the pass baffle may have a constantthickness in the region of the peripheral regions.

For stiffening the shell, in particular for strengthening the connectionbetween the shell parts of the shell, the heat exchanger has at leastone stiffening ring, which runs around on the shell transversely inrelation to the longitudinal axis and, in particular, is welded to theshell. It is preferably provided that the at least one stiffening ringreaches around the shell or, as an alternative to this, that the shellreaches around the stiffening ring, i.e. runs around on an inner side,facing the shell space, of the shell or of the two shell parts.

The pass baffle thus divides the shell space into a first portion, whichis made to extend along the longitudinal axis, and a second portion,which is made to extend parallel thereto and lies opposite to the firstshell portion. These two portions are connected to one another in aflow-directing manner preferably in the region of a first end portion ofthe shell space. The two portions of the shell space preferably alsorespectively surround an assigned part of the tube space (for examplethe tubes of a tube bundle respectively running in the portionconcerned), so that the first medium, carried in the two portions, canenter into indirect heat exchange with the second medium, carried in therespectively assigned part of the tube space.

For introducing the first medium into the first portion of the shellspace, an inlet, for example in the form of a connection piece, ispreferably provided on the shell, at a second end portion of the shellspace that lies opposite from the first end portion of the shell spacealong the longitudinal axis. Furthermore, provided opposite from that onthe shell, at the second end portion of the shell space, is an outlet,by way of which the first medium can be withdrawn from the secondportion of the shell space. The first medium, introduced into the firstportion, can consequently flow along a first direction to the first endportion of the shell space and then flow along an opposite seconddirection in the second portion (back) to the outlet for withdrawing thefirst medium.

In order to be able to deflect the flow of the first mediumperpendicularly in relation to the longitudinal axis, so that forexample a cross-counterflow is possible with respect to the secondmedium that is conducted in the tube space, there are preferablyprovided a number of sheet-like cross baffles, which are arranged in thetwo portions of the shell space and correspondingly extend respectivelyperpendicularly away from the pass baffle, and are thereby preferablyoriented perpendicularly in relation to the longitudinal axis.Neighboring cross baffles are preferably respectively arranged offset inrelation to one another, so that the first medium flows through the twoportions of the shell space in a meandering manner. The cross bafflesare preferably fixed to the pass baffle, to be precise in particular bywelding. In principle, the cross baffles may be variably distributed orarranged in the shell space (depending on the application).

The tube space preferably has a tube bundle, arranged in the shellspace, or is formed by such a tube bundle, the tube bundle having atleast a first tube, running along the longitudinal axis, and at least asecond tube, running along the longitudinal axis, which tubes areconnected to one another (in one piece) by way of a U-shaped tubeportion in the region of the first end portion of the shell space. Thetwo tubes are anchored at a respective free end, lying opposite from theU-shaped tube portion, in a tube sheet of the tube bundle that is madeto extend perpendicularly in relation to the longitudinal axis, andparticularly bounds the shell space and separates it from a head of theheat exchanger. The tube bundle preferably has a plurality of such pairsof first and second tubes connected by way of a plurality U-shaped tubeportions.

The head of the heat exchanger is preferably divided into an inletchamber and an outlet chamber, it being possible for the second mediumto be introduced into the tube space or the tube bundle by way of theinlet chamber and by way of the tube sheet, and it being possible forthe second medium to be drawn off from the tube space and out of theheat exchanger by way of the outlet chamber. An inlet, particularlyprovided on the shell, is connected to the inlet chamber in aflow-directing manner and is intended for introducing the second mediuminto the inlet chamber. In addition, an outlet, particularly provided onthe shell, is connected to the outlet chamber in a flow-directing mannerand is intended for withdrawing the second medium from the outletchamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and advantages of the invention are to be explained withthe following description of the Figures of exemplary embodiments on thebasis of the figures, in which:

FIG. 1 shows a schematic sectional view of a heat exchanger according tothe invention;

FIG. 2 shows a section through the shell space of the heat exchangeraccording to FIG. 1 along the line II-II of FIG. 1;

FIG. 3 shows a partly sectioned view of the heat exchanger shown inFIGS. 1 and 2 along the line III-III of FIG. 1;

FIG. 4 shows a sectional view in the manner of a detail of the heatexchanger shown in FIGS. 1 to 3;

FIG. 5 shows a detail of FIG. 3 or 4;

FIG. 6 shows a detail of FIG. 3 or 4 in an alternative embodiment;

FIG. 7 shows a sectional view of a heat exchanger according to theinvention, fitted with a stiffening ring, along the line VII-VII of FIG.1; and

FIG. 8 shows a sectional view of a modification of the heat exchangershown in FIG. 7 along the line VIII-VIII of FIG. 1.

FIG. 1 shows in conjunction with FIGS. 2 to 8 a heat exchanger 1, with apressure-bearing shell 10, which is made to extend along a longitudinalaxis L, which runs horizontally—with respect to a state of the heatexchanger 1 arranged as shown. The shell 10 is preferably given the formof a hollow circular cylinder (possibly apart from at the free ends ofthe heat exchanger 1), so that the longitudinal axis L is in particularcorrespondingly a cylinder axis.

The shell 10 defines a shell space M for receiving a first medium W,which is particularly water. The shell space M thereby encloses a tubespace R of the heat exchanger 1, which is designed for receiving asecond medium G, which is particularly a synthesis gas, so that thatsecond medium G can enter into indirect heat exchange with the firstmedium W, carried in the shell space M.

The tube space R is in this case formed by a tube bundle, which has aplurality of first and second tubes 61, 62, which are respectivelyconnected to one another by way of a U-shaped tube portion 63 and arerespectively anchored by free ends 611 and 621 in a tube sheet 6 of thetube bundle R. In the case of a hollow circular-cylindrical shell 10,the tube sheet 6 is correspondingly given the form of a circular sheet(disc-shaped). The tube sheet 6 bounds the shell space M and separatesfrom it a head K of the heat exchanger 1, which is divided into an inletchamber 301 and an outlet chamber 302 by means of a wall 312 made toextend along the longitudinal axis L. The head K of the heat exchanger 1is also bounded by a sheet 70, which can be fastened to the shell 10,for example by way of a flange, and lies opposite the tube sheet 6 alongthe longitudinal axis L.

The shell 10 of the heat exchanger 1 is mounted on an underlying surfaceby way of connection pieces 50, it being possible for one of theconnection pieces 50 to form a sliding bearing for the shell 10 tocompensate for thermally induced stresses.

For directing the first medium W along the longitudinal axis, the shellspace M is divided along that longitudinal axis L by a sheet-likerectangular pass baffle 20 into a first portion 201 and a parallelsecond portion 202, that communicates with the first portion 201. Thetwo portions 201, 202 are connected to one another in the region of afirst end portion 2 of the shell space M that lies opposite from thetube sheet 6 along the longitudinal axis L. The pass baffle 20 alsodivides the shell 10 into a first and a second shell part 101, 102,which are made to extend along the longitudinal axis L and respectivelyhave the form of a half shell. In particular, the two shell parts 101,102 are formed mirror-symmetrically in relation to one another, that isto say, for example, each forming half of a cylindrical shell.

The pass baffle 20 thereby also divides the tube bundle R into a firstpart and a second part. The first portion 201 of the shell space Msurrounds the first part of the tube space or the tube bundle R, and thesecond portion 202 of the shell space M surrounds the second part of thetube space or the tube bundle R. The free ends 611, 621 of the first andsecond tubes of the tube bundle R are accommodated here in the tubesheet 6 in such a way that the second medium G can be admitted to thetube bundle R by way of the tube sheet 6. For this purpose, the secondmedium G can be fed by way of an inlet 310, which is provided on thehead K and opens out into the inlet chamber 301 (hot side of the heatexchanger 1), into the inlet chamber 301 and from there into the firsttubes 61 of the tube bundle R (for example at about 300° C. in the caseof a synthesis gas G). The second medium G then flows along thelongitudinal axis L of the heat exchanger 1 towards the first endportion 2 of the shell space M, where the first tubes 61 go over by wayof the respectively assigned U-shaped tube portions 63 into the secondtubes 62 of the tube bundle R. The second medium G is then returnedthrough the second tubes 62 to the tube sheet 6 and enters the outletchamber 302, from which the second medium G can be withdrawn from theheat exchanger 1 by way of an outlet 311 (hot side, synthesis gas G atabout 200° C.).

The first medium W is thus carried in particular in cross-counterflow inrelation to the second medium G. Provided for this purpose in the regionof the tube sheet 6, at a second end portion 3 of the shell space M thatlies opposite from the first end portion 2 of the shell space M, is aninlet 210 (cold side of the heat exchanger 1). By way of inlet 210 thefirst medium W (feed water at for example 100° C.) can be introducedinto the shell space M, so that it flows along a direction E, headingtowards the first end portion 2, to that first end portion 2 in thefirst portion 201 of the shell space M, and then flows back in thesecond portion 202 along a direction E′, opposite in comparison with thefirst direction E, to the second end portion 3 of the shell space M.Provided there on the shell 10, adjacent to the tube sheet 6 (oppositethe inlet 210) is an outlet 211 (cold side of the heat exchanger 1), byway of which the first medium W can be withdrawn from the shell space M(for example said feed water at about 250° C.).

In order to be able also to conduct (divert) the first medium W in theshell space M transversely in relation to the longitudinal axis L, andcorrespondingly bring about a meandering flow of the first medium W inthe first and second portions 201, 202 of the shell space M, therepreferably extend perpendicularly away from the pass baffle 20 aplurality of cross baffles 40, which respectively connect the passbaffle 20 to an opposite inner side of the shell 10.

The cross baffles 40 are in this case particularly arranged offset inrelation to one another transversely in relation to the longitudinalaxis L according to FIG. 2, so that passages are formed between thecross baffles 40 and the inner side of the enclosing shell 10, therebyforcing the first medium W to flow not only along the longitudinal axisL but at the same time also back and forth transversely in relation tothe longitudinal axis L, as is indicated in FIG. 2 by the arrows (cf.also FIGS. 3 and 4).

The connection between the pass baffle 20 and the first and second shellparts 101, 102 is specifically formed in particular in the waycorresponding to FIGS. 5 and 6.

Accordingly, the two shell parts 101, 102, respectively, each have afirst end face 103, 104, made to extend along the longitudinal axis L,and a second end face (not shown in FIGS. 5 and 6; see 105, 106,respectively, in FIGS. 7-8). The first end face (103, 104) is in thiscase brought to lie against a respectively facing first or second side21 a, 21 b of a first outer peripheral region 21 of the pass baffle 20made to extend along the longitudinal axis L, those two sides 21 a, 21 bfacing away from one another.

The two second end faces 105, 106 correspondingly, lie on both sides ofa second outer peripheral region 22 (not shown in FIGS. 5 and 6) of thepass baffle 20 on a first and second side, respectively, of that secondperipheral region 22, which sides in turn face away from one another(cf. also FIGS. 7 and 8). The second peripheral region 22 of the passbaffle 20 runs parallel to the first peripheral region 21. The passbaffle 20 is consequently arranged transversely in relation to thelongitudinal axis L between the two shell parts 101, 102.

For forming a sealed connection between the pass baffle 20 and the twoshell parts 101, 102 along the longitudinal axis L, the first and secondend faces 103, 104 and 105, 106, respectively, are then welded to therespectively assigned side 21 a, 21 b of the respective peripheralregion 21, 22, so that a first, second, third and fourth weld seam 31-34result (cf. FIGS. 7 and 8). These four weld seams are respectivelyformed continuously in a direction oriented perpendicularly in relationto the longitudinal axis L. Hereafter, only the first and second weldseams 31, 32 according to FIGS. 5 and 6 are described. The third andfourth weld seams 33, 34 are of an analogous form (cf. FIGS. 7 and 8).

In the present case, “continuously” with respect to the weld seams meansthat the first and second end faces 103-106 are connected to the firstand second peripheral regions 21, 22, respectively, particularly overtheir full surface area by way of the assigned weld seams 31-34, so thata stable, sealed connection of the shell parts 101, 102, that can absorband withstand the pressure exerted on the shell parts 101, 102 by thefirst medium W conducted in the shell space M, is ensured all the wayalong the longitudinal axis L. Correspondingly, the first and secondweld seams 31, 32, respectively, have an outwardly facing outer side 31a, 32 a, which goes over into an outer side 101 a, 102 a of the assignedshell part 101 and 102, respectively. In the same way, the two weldseams 31, 32 each have an inner side 31 b, 32 b, which goes over into arespectively assigned inner side 101 b, 102 b of the corresponding shellpart 101, 102 and into an adjacent first side 20 a and an adjacentsecond side 20 b of the pass baffle 20.

According to FIG. 5, the first and second weld seams 31, 32 narrow incross section towards the shell space M, a step particularly beingformed, respectively on the inner side 101 b, 102 b of the assignedshell part 101, 102, so that the weld seams 31, 32 reach behind therespectively assigned inner side 101 b and 102 b of the shell part 101,102 concerned. Other cross-sectional forms are also conceivable.

FIG. 6 shows an alternative embodiment, in which, as a difference fromFIG. 5, the pass baffle 20 has a constant thickness in the region of thefirst and second peripheral regions 21, 22. By contrast, the first andsecond peripheral regions 21, 22 according to FIG. 5 are narrowed in theregion of the weld seams 31, 32 respectively towards an outer space Asurrounding the heat exchanger 11. This allows the effective connectingarea between the pass baffle 20 on the one hand and the shell parts 101,102 on the other hand to be increased.

Finally, as shown in FIGS. 7 and 8, the heat exchanger 1 mayadditionally have stiffening rings 80 for the shell 10.

According to FIG. 7, it is provided that such stiffening rings 80 reacharound the shell 10 transversely in relation to the longitudinal axis L,that is to say run around from the outer space A. For stiffening theshell 10, the stiffening ring or rings 80 are in this case preferablywelded around the periphery or at discrete points to the shell 10 or theshell parts. The stiffening rings 80 can in this case absorb the loadexerted on the shell 10 from the shell space M and support the weldseams 31 to 34.

As an alternative to this, according to FIG. 8 there is the possibilitythat the stiffening rings 80 run around the inside of the shell 10transversely in relation to the longitudinal axis L and are welded to itaround the periphery or at discrete points. In this case, correspondingclearances may be provided on the pass baffle 20, through which thestiffening rings 80 are led. Furthermore, according to FIG. 8, in across-sectional plane running perpendicularly in relation to thelongitudinal axis, weld seams 31, 34 may extend as far as the stiffeningrings 80 and correspondingly connect them to the shell 10 and/or passbaffle 20.

In comparison with the known technical teaching, throughputs in therange of particularly 80-100 m³/h can be achieved with the solutionaccording to the invention, for example, in a synthesis gasinstallation. The present connection between the pass baffle and theshell 10 leads to increased reliability of the process and ensures amore effective heat exchange between the tube side and the shell side ofthe heat exchanger 1.

Apart from synthesis gas installations, the heat exchanger 1 accordingto the invention may also be used in refineries or power generatingplants. Specifically in the refinery area, a low risk of bypassing flowsis desired. Other industries in the heat exchanger area may of coursesimilarly use the invention.

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples.

The entire disclosure[s] of all applications, patents and publications,cited herein and of corresponding German Application No. 10 2011 103635.4 filed Jun. 8, 2011, are incorporated by reference herein.

List of designations  1 Heat exchanger  2 First end portion  3 Secondend portion  6 Tube sheet  10 Shell  20 Pass baffle  20a First side  20bSecond side  21 First peripheral region  21a First side  21b Second side 22 Second peripheral region  22a First side  22b Second side  31 Firstweld seam  31a Outer side  31b Inner side  32 Second weld seam  32aOuter side  32b Inner side  33 Third weld seam  34 Fourth weld seam  40Cross baffles  50 Connection pieces  61 First tube  62 Second tube  63U-shaped end portion  70 Sheet  80 Stiffening ring 101 First shell part102 Second shell part 201 First portion 202 Second portion 210 Inlet 211Outlet 301 Inlet chamber 302 Outlet chamber 310 Inlet 311 Outlet 312Wall 611 Free end 621 Free end A Outer space E First direction E′ Seconddirection G Second medium K Head L Longitudinal axis M Shell space RTube space, tube bundle W First medium

1. A heat exchanger for providing heat exchange between a first and asecond medium (W, G), comprising: a shell (10), extending along alongitudinal axis (L), which bounds a shell space (M) for receiving afirst medium (W), a tube space (R), surrounded by said shell space (M),for receiving a second medium (G), and a pass baffle (20), arranged insaid shell space (M) and made to extend along said longitudinal axis(L), for directing first medium (W) carried in said shell space (M)along said longitudinal axis (L), wherein said pass baffle (20) iswelded to said shell (10).
 2. The heat exchanger according to claim 1,wherein said shell (10) has a first shell part (101), which is made toextend along said longitudinal axis (L), and a second shell part (102),which is made to extend along said longitudinal axis (L) and liesopposite to said first shell part (101) transversely in relation to saidlongitudinal axis (L), the two shell parts (101, 102) being connected toone another with said pass baffle (20) interposed.
 3. The heat exchangeraccording to claim 2, wherein said pass baffle (20) has a firstperipheral region (21) with a first side (21 a), which faces said firstshell part (101), and a second side (21 b), which is remote from saidfirst side (21 a) and faces said second shell part (102), said firstshell part (101) being connected by a first end face (103), made toextend along said longitudinal axis (L), to said first side (21 a) ofsaid first peripheral region (21) by way of a first weld seam (31), andsaid second shell part (102) being connected by a first end face (104),made to extend along said longitudinal axis (L), to said second side (21b) of said first peripheral region (21) of said pass baffle (20) by wayof a second weld seam (32).
 4. The heat exchanger according to claim 3,wherein said pass baffle (20) has a second peripheral region (22) with afirst side, which faces said first shell part (101), and a second side,which is remote from said first side and faces said second shell part(102), said first shell part (101) being connected by a second end face(105), made to extend along said longitudinal axis (L), to said firstside of said second peripheral region (22) by way of a third weld seam(33), and said second shell part (102) being connected by a second endface (106), made to extend along said longitudinal axis (L), to saidsecond side of said second peripheral region (22) of said pass baffle(20) by way of a fourth weld seam (34).
 5. The heat exchanger accordingto claim 4, wherein the two peripheral regions (21, 22) lie opposite oneanother transversely in relation to the longitudinal axis (L).
 6. Theheat exchanger according to claim 3, wherein said weld seams (31-34) areformed continuously in a cross-sectional plane running perpendicularlyin relation to said longitudinal axis of said shell (10), so that saidweld seams (31-34) respectively have an outer side (31 a-34 a), whichfaces an outer space (A) surrounding the shell (10), is adjacent theretoand goes over into an outer side (101 a, 102 a) of the respectivelyassigned shell part (101, 102) of said shell (10), and said weld seams(31-34) also respectively an inner side (31 b-34 b), which faces theshell space (M), is adjacent thereto and goes over into an inner side(101 b, 102 b) of the respectively assigned shell part (101, 102) ofsaid shell (10) that faces said shell space (M) and goes over into arespectively assigned side (20 a, 20 b) of said pass baffle (20).
 7. Theheat exchanger according to claim 3, wherein, in a cross-sectional planerunning perpendicularly in relation to said longitudinal axis (L) ofsaid shell (10), said weld seams (31, 34) initially narrow towards saidshell space (M) and widen again in the region of an inner side (101 b,102 b), facing said shell space (M), of the respectively assigned shellpart (101, 102), so that said weld seams (31, 34) reach behind saidinner sides (101 b, 102 b) of the respectively assigned shell part (101,102).
 8. The heat exchanger according to claim 3, wherein said passbaffle (20) narrows at said peripheral regions (21, 22) towards an outerspace (A) surrounding said shell (10).
 9. The heat exchanger accordingto claim 3, wherein said pass baffle has a constant thickness at saidperipheral regions (21, 22).
 10. The heat exchanger according to claim1, wherein said heat exchanger (1) has at least one stiffening ring(80), which runs around on said shell (10) transversely in relation tothe longitudinal axis (L) and in particular is welded to the shell (10),the at least one stiffening ring (80) particularly reaching around theshell (20) or the shell (10) reaching around the stiffening ring (80).11. The heat exchanger according to claim 1, wherein said pass baffle(20) divides said shell space (M) into a first portion (201), which ismade to extend along said longitudinal axis (L), and a second portion(202), which is made to extend along said longitudinal portion (L) andlies opposite said first portion (201), the two portions (201, 202)being connected to one another in a flow-directing manner particularlyin the region of a first end portion (2) of said shell space (M), andthe two portions (201, 202) respectively surrounding an assigned part ofsaid tube space (R), so that first medium (W), carried in the twoportions (201, 202), can enter into indirect heat exchange with secondmedium (G), carried in the respectively assigned part of said tube space(R).
 12. The heat exchanger according to claim 11, wherein an inlet(210), for introducing first medium (W) into said first portion (201) ofsaid shell space (M), and an outlet (211), for withdrawing first medium(W) out of said second portion (202) of said shell space (M), areprovided on said shell (10), at a second end portion (3) of said shellspace (M) that lies opposite from said first end portion (2) of saidshell space (M) along said longitudinal axis (L).
 13. The heat exchangeraccording to claim 1, wherein heat exchanger (1) has a plurality ofcross baffles (40), which are arranged in said shell space (M) and aredesigned and intended to deflect first medium (W), carried in said shellspace (M) transversely in relation to said longitudinal axis (L),neighboring cross baffles (40) particularly being arranged offset inrelation to one another, and said cross baffles (40) particularlyextending respectively perpendicularly away from said pass baffle (20),and said cross baffles (40) particularly being fixed to said pass baffle(20), in particular welded to it.
 14. The heat exchanger according toclaim 1, wherein said tube space (R) of said heat exchanger (1) isformed by a tube bundle arranged in said shell space (M), said tubebundle (R) having at least a first tube (61), running along thelongitudinal axis (L) and at least a second tube (62), running along thelongitudinal axis, which tubes are connected to one another by way of aU-shaped tube portion (63), the two tubes (61, 62) being anchored at arespective free end (611, 621), lying opposite from said U-shaped tubeportion (63), in a tube sheet (6) of said tube bundle (R).
 15. The heatexchanger according to claim 14, wherein said tube sheet (6) separatessaid shell space (M) from a head (K) of said heat exchanger (1).
 16. Theheat exchanger according to claim 15, wherein said head (K) is dividedinto an inlet chamber (301) and an outlet chamber (302), wherein secondmedium (G) can be introduced into said tube space (R) by way of saidinlet chamber (301), and wherein second medium (G) can be withdrawn fromsaid tube space (R) and out of the heat exchanger (1) by way of saidoutlet chamber (302), an inlet (310), which is connected to the inletchamber (301) and is provided for introducing second medium (G) intosaid inlet chamber (301), and an outlet (311), which is connected to theoutlet chamber (302) and is provided for withdrawing second medium (G)out of said outlet chamber (302), particularly said inlet (310) and saidoutlet (311) being provided on said shell (10).